A take-profit is a pre-set price target where you exit a winning trade. Like a stop-loss but in the opposite direction — set the order with the broker, walk away, let the market hit it or not.
The discipline is symmetric to stops: a take-profit makes you pre-commit to a finite gain rather than chasing the trade indefinitely. The math says you can't have profit factor without exiting winners somewhere; the question is whether 'somewhere' is a planned level or a panic decision.
Most traders move their take-profits later in the trade. The reasons traders give are analytical — 'momentum is strong,' 'the level looks weak,' 'there's more in the move' — but the journal almost always reveals the reasons are emotional. Greed is more comfortable than locking in a known winner; cognitive dissonance after a 'small' win feels worse than risking the entire gain. The data is brutally consistent on this.
Common implementations: a single full-exit target (simple, robust), a partial profit at 1R plus a runner (captures both the high-probability win and the occasional outlier), or a structural exit (next swing high, prior pivot, measured move). Each works; what matters is having one and honoring it. The traders who outperform aren't picking better targets — they're moving them less.